This is an evil and horrible speed hack. Basically, if you have a big
chunk of XML that you want to insert into the DOM, but you don't want to
incur the cost of parsing it, you can construct one of these and insert it
into the DOM. This will most certainly only work with microdom as the API
for converting nodes to xml is different in every DOM implementation.

This could be improved by making this class a Lazy parser, so if you
inserted this into the DOM and then later actually tried to mutate this
node, it would be parsed then.